RESUMEN
The development of respiratory infection indicates either a defect in host defenses, exposure to a particularly virulent microorganism, or an ovenwhelming inoculum, as infectious agents gain entry to the lower respiratory tract through aspiration of upper airway resident flora. Better prognosis of patients with leukaemia over the last decade is at least partly due to the possibility of administering more intensive chemotherapy and to the successful introduction a wider array of antimicrobials. To evaluate the antimicrobial susceptibility of the isolates of both leukaemic and non-leukaemic patients with. LRTIs. The present study consisted of 50 adult leukaemic patients, 14 males and 36 females beside other 50 adult non-leukaemic patients, 25 males and 25 females were included, who were admitted to Baghdad Teaching Hospital, through the period from December 2003 through May 2004 with diagnosis of LRTIs. The antimicrobial susceptibility test was done upon the bacterial isolates according to Kirby-Bauer method. The most reliable antibiotics among leukaemic patients [acute myelogenous, acute lymphoblastic, chronic myeloid, chronic lymphocytic] according to antimicrobial susceptibility test, were in cosequence, ciprofloxacin, followed by cefotaxime, then gentamicin and equal influence by ceftriaxone, amikacin, cloxacillin followed by. trimethoprime-sulphamethoxazole, ampicillin, augmentin, finally by erythromycin. On the other spectrum, the most reliable antibiotics among non-leukaemic patients were in consequence ciprofloxacin, followed by trimethopritne-sulphamethoxazole, cefotaxime, an equal effect by ampicillin, gentamicin, and ceftriaxone, followed by augmentin, also an equal effect by cloxacillin and amikacin, finally by erythromycin. Antibiotic susceptibility test should be done for each bacterial isolate in order to prevent the development of progressive microbial resistance